1872.] SOLLAS UPPER- GREENSAND VENTRICULIT-EI. 69 



contain. He states that while Brachiolites are found in the Lower 

 Chalk and Upper Greensand, Ventriculites are confined to the Upper 

 Chalk alone, occurring very doubtfully in the Middle Chalk, if at all ; 

 the identifications in this paper, however, show that the genus Ven- 

 triculites not ouly is not confined to the Upper Chalk, but is found 

 abundantly as low as the Gault in England (for these Upper Green- 

 sand specimens are derived from the Gault) and still lower in the 

 White Jura of the Continent. The occurrence of* Ventriculites in 

 the Oolitic formation does not tend to strengthen the affinities of 

 the Chalk with our own times. 



The analogy I drew in a former paper between the flints of the 

 chalk and the coprolites of the Gault, receives illustration from these 

 newly discovered Ventriculites ; for precisely as the silicified Ven- 

 triculites are closely associated with obscure siliceous nodules or 

 flints, and, with them, are instances of that remarkable fact the silici- 

 fication of highly decomposable animal matter; so the phosphatic 

 Ventriculites are closely associated with obscure phosphatic nodules 

 or coprolites, and, with them, are striking examples of the phospha- 

 tization of soft-bodied animals. 



For the valuable assistance I have constantly received throughout 

 the preparation of this paper, my thanks are due and heartily tendered 

 to the Rev. Mr. Bonney, of St. John's College. I have also much 

 pleasure in thanking Mr. Jukes Browne (St. John's) and Mr. Jesson 

 (Trin. Coll.), to whom I am indebted for many interesting specimens 

 of our Cambridge Ventriculites. 



Discussion. 



Mr. J. F. Walker was not prepared to admit that all phosphatic 

 nodules had been organized bodies, inasmuch as most of the fossil 

 shells in the deposit were found filled with phosphatic mud of the 

 same nature as the nodules. 



Mr. Charlesworxh also disputed the organic origin of the amor- 

 phous coprolites — and pointed out the analogies between the so- 

 called coprolites of the Crag and those of the Upper Greensand, and 

 the flints of the Chalk. He cited Ehrenberg as of opinion that the 

 latter were masses of fossilized infusoria, while Dr. Bowerbank 

 maintained that they were merely fossil sponges ; and he drew the 

 deduction that caution was necessary in accepting any theory as to 

 the origin of the phosphatic nodules. 



Mr. Seelet was not entirely in accord with Mr. Fisher as to the 

 number of forms assumed by the phosphatic nodules. There were 

 some that resembled common septaria; and in many cases the 

 original form, especially in the case of the presumed Ventriculites, had 

 been much modified by rolling on the sea-bottom. In support of the 

 view of the sponge-origin of some of the nodules, he exhibited some 

 of the modern forms of sponges enveloping different objects in the 

 same manner as the phosphatic matter included shells and other 

 fossils. Some of the Porospongice in the Woodwardian Museum were, 

 he said, not phosphatic, but calcareous fossils ; and he thought some 

 mistake had been made by Mr. Sollas in alluding to these specimens. 



